Is the training computer, that uses GymLink transmission, within 1 meter/ 3.3 feet range from the heart rate sensor?

If you have a Polar T31 transmitter, make sure that there are no other heart rate sensors with GymLink transmission, within 1 meter/ 3.3 feet radius. Check here what type of transmission your training computer uses.

Are the heart rate signals unusually high or otherwise abnormal?
Relocating the training computer or adjusting the heart rate sensor on your body may help. For a list of possible sources of disturbance, see Abnormal Heart Rate Readings During Exercise.

Has the battery been changed by an unauthorized party? For some Polar training computer models you can change the battery yourself, for others Polar authorized service is recommended. See more here.

Does the ECG signal strength vary?
ECG signal strength varies depending on the individual’s tissue composition. The percentage of people who experience difficulties measuring heart rate is higher in water environment than in normal use.

Were you using the training computer in, or near seawater or a swimming pool? Have the buttons been pressed under water?
Seawater and swimming pool chemicals can affect ECG signal reception. Do not press buttons under water as it may cause leaking. For more on Polar products in water, see Polar Products in Water Environment.

Is the display frozen?
If the display has frozen, try resetting it. See user manual for instructions.

If the above information did not help, please contact your local Polar Service here.